1. Field of the Invention
The present invention relates generally to suspension systems for steerable wheels of vehicles such as automobiles and other self-propelled and towed vehicles such as trucks, tractors, off-the-road vehicles, four-wheel trailers and the like.
2. Prior Art
Steering gear systems have been proposed which employ wheels journaled on stub axles with the stub axles supported pivotally on king pins having axes that tilt downwardly and forwardly such that the wheels are caused to tilt into a turn to equal degrees during steering of the wheels. Proposals of this type are described in Weston U.S. Pat. Nos. 2,150,199 and Kost et al., 2,631,867.
In some previous proposals, the front axle is in clevis form and receives a quill formed at the end of a wheel spindle to receive a king pin. The king pin is arranged with its axis tilting outwardly and downwardly from the center of the front axle. Connecting rods are provided for controlling the angular position of the wheel spindles from a steering wheel. Such arrangements have been proposed in order to provide a castering suspension for the steerable wheels with the objective of causing the wheels to return to a forward traveling position if the operator's hold on the steering wheel is released. A proposal of this type is described in Eckenrode U.S. Pat. No. 2,115,256.
In order to enhance driving safety, to render a vehicle more sure footed in its stance, to make the suspension system more effective in high speed turns, to obtain more nearly equal wear on tires, to eliminate sway on turns, and to keep the vehicle on an even keel, it is desirable to provide an arrangement in which the king pin axis intersects the tread of its associated tire and preferably intersects substantially the area of contact between the tire and the road. In turning the vehicle, the wheel preferably pivots about an axis which intersects the area where the tire tread contacts the road, and, at the same time, tilts into the turn to enhance stability and performance. It is also desirable for purposes of strength and stability to support the wheel spindle of a steerable wheel at two locations spaced on opposite sides of the wheel rotation axis. Prior proposals have not recognized the desirability of this combination of features nor suggested its use.